If you get a bottle of vodka from your local liquor store, you’ll probably see two different numbers telling you how much alcohol it contains. The first is an alcohol by volume (ABV) percentage, which is relatively intuitive to understand: it’s the percentage of alcohol in the overall liquid and is pretty standard internationally. The other measurement is proof, a measurement of alcohol content that varies from country to country. The proof measurement harks back to 16th-century England, when the government would put an extra tax on “proof spirits”—that is, liquor that contained a certain higher amount of alcohol.

The word proof is used in the sense of showing that something is true or correct. The English government would test the amount of alcohol content in a liquor by soaking a gun pellet with it and attempting to light the wet pellet on fire. If the wet gunpowder could be lit, the alcohol was said to be a proof spirit and would therefore be taxed higher. This proofing method had a problem: the flammability of the liquor was dependent on its temperature. Since the temperature wasn’t kept consistent, this method for determining a proof spirit wasn’t accurate.

In 1816, England fixed this problem by standardizing its threshold for a proof spirit. A proof spirit was now a liquor with an alcohol level ¹²⁄₁₃ the weight of an equal volume of distilled water at 11 °C (51 °F). This specific gravity corresponds to about 57.06% ABV. This standardization became incorporated in Great Britain’s 1952 Customs and Excise Tax.

England made the proofing system a bit confusing. When the alcohol industry took hold in the U.S., Americans took a different approach to the measurement system. Stateside, a liquor’s proof is two times the ABV. So this means that a beverage with 30% ABV is 60 proof. A “proof spirit” has to be at least 100 proof.

The simplest proof scale, however, is the one used in France, developed by French scientist Joseph-Louis Gay-Lussac in 1824. Gay-Lussac took 100% ABV to equal 100 proof and 100% water by volume to be 0 proof. This means that the ABV percentage number is the same as the proof number.

So, to compare the three proof scales: an alcohol with 45% ABV is about 78.9 proof in Great Britain, 90 proof in the U.S., and 45 proof in France.

What’s the Difference Between an Herb and a Spice?

The use of herbs and spices can be found as far back as prehistoric times, often as valuable forms of currency in trade. The seasonings have also been used for medicinal properties and as preservatives in food storage. Many spices have been found to contain antimicrobial properties that thwart the growth of bacteria. You probably use some herbs or spices daily, but do you know the difference? The terms herb and spice are often used interchangeably, but they are in fact two distinct types of seasonings, made from different sections of plants and processed in different ways. So what are the qualities that distinguish an herb from a spice?

Let’s use cinnamon and oregano as examples. Cinnamon is a powdered spice that can be made from the bark of a few different trees that fall under the genus Cinnamomum. Spices like cinnamon are made from the aromatic seeds, bark, flowers, and roots of plants that have been dried and crushed. Oregano, however, is an herb derived from the herbaceous oregano plant. Herbs are leaves, and although most come from herbaceous plants (plants that lack woody stems), a few do come from woody plants, such as bay leaf. Basil, rosemary, and parsley are often found in a kitchen’s spice rack but actually qualify as herbs because they are aromatic leaves.

Spices tend to be stronger in flavor than herbs, because they are made from crushed portions of plants that are especially rich in essential oils. Herbs can be found either fresh or dried, chopped or whole.